32,027 research outputs found

    Hydrodynamic crystals: collective dynamics of regular arrays of spherical particles in a parallel-wall channel

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    Simulations of over 10310^3 hydrodynamically coupled solid spheres are performed to investigate collective motion of linear trains and regular square arrays of particles suspended in a fluid bounded by two parallel walls. Our novel accelerated Stokesian-dynamics algorithm relies on simplifications associated with the Hele--Shaw asymptotic far-field form of the flow scattered by the particles. The simulations reveal propagation of particle-displacement waves, deformation and rearrangements of a particle lattice, propagation of dislocation defects in ordered arrays, and long-lasting coexistence of ordered and disordered regions.Comment: 4 pages 6 figure

    The effects of deviate internal representations in the optimal model of the human operator

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    Some of the issues and equations involved in predicting closed-loop man machine performance for situations in which the human operators' knowledge of the system and/or environment are imperfect are presented and discussed. Several examples to demonstrate some of the effects to be expected when such is the case are then given

    Performance of a ballute decelerator towed behind a jet airplane

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    An F-104B airplane was modified to investigate the drag and stability characteristics of a ballute decelerator in the wake of an asymmetrical airplane. Decelerator deployments were initiated at a Mach number of 1.3 and an altitude of 15,240 meters (50,000 feet) and terminated when the airplane had decelerated to a Mach number of 0.5. The flight tests indicated that the decelerator had a short inflation time with relatively small opening forces. The drag levels attained with the subject decelerator were less than those obtained with other high-speed decelerators behind a symmetrical tow vehicle. The ballute demonstrated good stability characteristics behind the testbed airplane

    Arcuate nucleus homeostatic systems reflect blood leptin concentration but not feeding behaviour during scheduled feeding on a high-fat diet in mice

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    Acknowledgements T.B. was funded by a CASE studentship from the BBSRC and AstraZeneca. J.B. was a summer student from Bordeaux Sciences Agro and funded by student laboratory experience grant from the British Society of Neuroendocrinology. The authors are also grateful for funding from the Scottish Government, and from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreements 266408 (Full4Health) and 245009 (NeuroFAST).Peer reviewedPublisher PD

    Feasibility of an Incoherent-scatter Radar Aboard the Space Shuttle

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    The results of a preliminary study to investigate the feasibility of conducting an incoherent scatter radar experiment on board the space shuttle are presented. The results indicate that such an experiment is technically feasible. The more difficult questions to answer are whether the system can be made flexible enough to justify the problems and costs involved. The design parameters and the tradeoffs that are available in the consideration of these questions are evaluated. Some of the more serious limitations pertain to: (1) the presence of ground clutter and F region auroral clutter; (2) available average power; (3) weight and volume associated with required antenna size, transmitter, and energy storage devices; and (4) antenna breakdown associated with high power transmitter problems